1. Field of the Invention
The present invention relates to a heat sink fan for cooling a heat generating device such as an electric device, and more particularly, relates to a heat sink fan for cooling an electronic device such as a semiconductor device, for example, a CPU (central processing unit) or a microprocessor and an electronic circuit or the like.
2. Description of the Related Art
Heat sink fans have been used for cooling an electric device such as a CPU or the like which generates heat during the operation. The heat sink fan includes a heat sink made of heat conductive material such as aluminum or the like and having a plurality of radiation fins and a housing attached to the heat sink so as to cover the upper portion of it and form an opening communicating between an interior of the housing and the outside air. A fan motor having a rotor on which a plurality of fan blades are formed, is disposed within the housing. The heat sink is attached to the electric device with one of its surfaces being in close contact with the device.
When the fan motor having a plurality of fan blades rotates, outside air is sucked into the housing through the opening of the housing and passes by the respective radiation fins of the heat sink. The heat is conducted from the electric device to the heat sink and is radiated by the outside air passing by the respective radiation fins to suppress temperature rise in the electric device.
However, as the electric device such as semiconductor devices, a CPU, a microprocessor and an electronic circuit or the like, is improved in performance, for example, in operating speed, processing speed or the like, the amount of heat generated by the electric device increases so that the conventional heat sink does not work sufficiently. If the electric device is not cooled sufficiently, its temperature rises, resulting in not only deterioration in performance but also damage to the electric device. To be adapted for such electric device of improved performance, the heat sink fan must be improved in heat radiation efficiency to cool the electric device sufficiently.
The radiation efficiency of the heat sink fan depends upon the material of the heat sink and the capacity of the fan motor. However, if the rotational speed of the fan motor is increased to increase the capacity of the fan motor, there arises a new problem that the noise generated by the fan motor and the electric power consumption for rotating the fan motor are increased.
The heat sink is generally made of aluminum or aluminum alloy. This is because aluminum or aluminum alloy have a good heat conductivity and is excellent in workability and cost. Accordingly, it is difficult to greatly improve the cooling performance of the heat sink fan by using other material without reducing the workability and the cost.